Concanavalin A binds specifically to chromatin. Electrophoresis in polyacrylamide gels in the presence of SDS reveals that 80% of the concanavalin A binding capacity is localized in one non-histone protein with an apparent molecular weight of 135,000. Fluorescence and autoradiographic studies reveal that this lectin binds to specific loci in polytene chromosomes. The binding site may change during the life cycle of a cell. Attempts are being made to isolate the con-A receptor. Glycoproteins may have important functions for various recognition phenomena important for proper functioning of chromosomes and chromatin.